Resistance welding of sheet metal coated with layers

ABSTRACT

The invention relates to a method for the resistance welding of sheet metal coated with layers, wherein firstly electrical contact is established between the sheets to be interwelded and between the welding electrodes and said sheets, and subsequently welding is effected across the coating layers. The invention relates also to machines for carrying out this method.

United States Patent 1151 3,643,057 Becker [4 1 Feb. 15, 1972 [54] RESISTANCE WELDING OF SHEET 7 7 km METAL COATED WITH LAYERS UNITED mcp g m [721 m 3,337,711 8/1967 Garscia "1219/92 *Gemy 3,277,268 10/1966 Williams etal. ..219/92 F' 1968 FOREIGN PATENTS OR APPLICATIONS 1 a 697,396 9/1953 Great Britain......., ..219/91 [30] Fmign Application Priority on Primary Examiner-J. V. Truhe Feb. 11, 1967 Germany ..B 91 162 Assistant g Smith May 26, 1967 Germany... Attorney-Each M. H. Radde Apr. 24, 1967 Germany.;. Feb. 27, 1967 Germany I [57] ABSTRACT v v I The invention relatestoamethod for the resistance welding of g1 Univ/9 1 11962: sheetmemcomd wimayemwherein filmy electrical com [58] i tact is established between the sheets to beinterwelded and between me welding electrodes and said sheets, and my sequently welding is effected across the coating layers. The invention relates also to machines for carrying out this method.

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1. A method for resistance welding of insulation-coated sheet metal to at least one other coated sheet metal comprising initially establishing shunts from each of the electrodes to spaced points on the respective sheet metals which each electrode will subsequently contact, providing spaced contact points between the adjacent faces of the sheet metals to be welded together, passing current from the shunts through the sheet metals by way of the electrical contacts interconnecting the faces so that the insulation material is melted, and subsequently welding the sheet metals together through the electrodes.
 2. A method according to claim 1 wherein said shunt comprises passing a shunt line from an upper electrode to the upper sheet metal, passing a shunt line from the lower electrode to the lower sheet metal, and wherein said contact points are provided by interposing an intermediate welding piece between the bare internal surfaces of said two superimposed sheet metals coated only on one side each.
 3. A method according to claim 1 wherein said welding step comprises contacting the upper electrode to a stripped are of the upper sheet metal.
 4. A method according to claim 1 wherein several sheet metals are welded together and said contact points are auxiliary contacts located at opposite ends of the sheet metals, and each auxiliary contact passing through only a part of said several sheet metals.
 5. A method according to claim 1 wherein a packet of superimposed sheet metals is welded together and said contact points are auxiliary contacts passing through said sheet metals.
 6. A method according to claim 1 comprising regulating the current in the shunt line by means of a control resistor.
 7. A method according to claim 1 wherein a plurality of sheet metals is welded together and said shut lines pass alternately from the upper electrode and from the lower electrode to the sheet metals.
 8. A method according to claim 1 wherein providing said contact points comprises placing a spacer between the bare surfaces of sheet metals coated on one side only.
 9. A method according to claim 1 wherein a plurality of metals is welded together and said shunt lines pass alternately from the upper and lower electrodes to said sheet metals and inserting filler welding pieces in external stripped areas provided between the electrodes and their adjacent sheet metals, and wherein providing said contact points comprises inserting intermediate welding pieces between sheet metals.
 10. A method according to claim 1 for establishing contact between an electrode and a coated sheet metal comprising inserting a pressed-in wire between an electrode and a coated sheet metal.
 11. A method according to claim 1 wherein said shunt lines comprise contact tubes on the sheet metal spaced from said electrodes, opposite tubes being connected to opposite electrodes. 